The medical aid group Doctors Without Borders has suspended its work in prisons in the Libyan city of Misrata because it says detainees are being tortured.

The group, also known by its French name Medecins Sans Frontieres, said that since August its medical teams have treated 115 people in Misrata who bore torture-related wounds.

These included cigarette burns, heavy bruising, bone fractures, tissue burns from electric shocks, and renal failure from beatings. Two detainees died after being interrogated, the group's director general said.

"Patients were brought to us in the middle of interrogation for medical care, in order to make them fit for further interrogation. This is unacceptable," MSF general director Christopher Stokes said.

"Our role is to provide medical care to war casualties and sick detainees, not to repeatedly treat the same patients between torture sessions."

There was no immediate response from Libyan authorities, but the allegations were an embarrassment for the country's new leaders, who have promised to respect human rights and end the rampant abuses of the Gaddafi regime.

Britain, which played a key role in the Nato-led air campaign that helped revolutionary forces overthrow long-time dictator Muammar Gaddafi, urged Libya's National Transitional Council to "live up to the high standards they have set themselves."

"They need to ensure a zero tolerance policy on abuse. We are concerned about these reports and are taking the up with the Libyans as a matter of urgency," British Prime Minister David Cameron's office said in a statement.

Stokes said those subjected to torture include ex-combatants and people accused of theft and looting.

The interrogations were carried out by Libya's National Army Security Service at facilities outside the detention centres, MSF said in a statement.